April Tree of the Month: Lemon-Scented Gum

By David Gress

Perhaps the first thing you notice about a Lemon-Scented Gum tree is its unique bark – pinkish-white and perfectly smooth.  A real eye-catcher.

For quick identification, other striking features are its long trunk and, topping that, the up-reaching open branch structure with graceful pendulous branchlets, all of which make a beautiful silhouette against the sky.  It’s hard to miss a mature tree, since it can easily reach over 100 feet in height with a crown spread of over 90 feet in width!

The best way to remember the first part of its common name is to pick a leaf, crush it between your fingers, sniff its broken margins, and instantly experience its refreshing lemon scent – a delightful dose of aromatherapy!  “Gum” refers to the fact that sap oozing from any wounds in the bark is quite gummy and sticky.

The Lemon-Scented Gum is native to the dry woodlands of Queensland, Australia.  It was brought to California in the late 1880’s – and was first planted locally by Ellwood Cooper in 1887 at his ranch west of Goleta (part of which is now the Ellwood Preserve).  One of his trees has grown to be the largest of its kind in California – with a height exceeding 140 feet, a crown spread of over 95 feet, and a trunk nearly 14 feet in circumference!  Early in the last century, it was crowned the “Ellwood Queen” and today, at age 133, it still stands as a truly regal specimen.

Mature leaves are glossy green on both sides and measure and 1/3 to 1 inch wide and 3 to 6 inches long; these are often sickle-shaped.  Curiously, juvenile leaves are larger, at 1 to 3 inches wide and 4 to 7 inches long; these can be rough and bristly from long oil glands and, as a result, are the most strongly scented.

Through late winter and spring, its small white flowers appear in dense clusters along the branchlets.  The fuzzy-looking flowers offer copious amounts of pollen and nectar, which are very attractive to bees who, not surprisingly, make from them a delicious honey.  The pollinated flowers develop into woody, urn-shaped capsules, ½ inch long, which are filled with tiny seeds. 

Currently, there are no serious insect or disease problems with this tree species.  In the not-too-distant past, though, it did suffer from invasion by a serious insect pest, the “lerp psyllid”, a bug as nasty as its name sounds.  Fortunately, this psyllid seems to have been controlled through the release of great numbers of a parasitic wasp, a natural predator.  Biological warfare at its best!

Lemon-Scented Gum is very well suited to our Mediterranean climate.  It can grow in a wide variety of soil conditions and is quite drought-tolerant when established.  Due also to its elegant and graceful appearance, it has proved to be very popular.  Consequently, over the years, it has been planted extensively, as an ornamental tree, throughout Santa Barbara County and California.

Besides its value as a landscape tree, the Lemon-Scented Gum has many useful purposes.  The leaves and sap contain the chemical citronellal, which is processed into essential citronella oils used in perfumes, menthols, insect repellents, and aboriginal and traditional medicines.  In Australian, its wood is highly prized for tools and lumber.

Its botanical name is Corymbia citriodora.  The genus name, “Corymbia”, refers to its corymb-type flower clusters.  The specific epithet, “citriodora”, refers to its lemon-citrus odor.  Most folks think Lemon-Scented Gum is still in the genus Eucalyptus; but, it’s only a close relative.  After genetic testing, it was reclassified into the genus Corymbia.

Because of its potentially large size at maturity, a Lemon-Scented Gum should be placed in a location that can accommodate its ultimate growth.  It should be planted in a sunny location.  Note: a young tree will require adequate staking, to allow the trunk and roots to sufficiently develop before the tree is subject to buffeting winds.

Besides the “Ellwood Queen”, there are several well-known and historic Lemon-Scented Gums in Santa Barbara.  The oldest and largest, the “Fernald Eucalyptus”, standing on the east side of the 400 block of Santa Barbara Street, was saved by Pearl Chase when that block was being developed.  The old trees in front of the Central Library downtown have been designated historic landmarks by the City.  Other outstanding specimens can be seen on upper State Street at Calle Real, in the parking lot of 5 Points Shopping Center, on State Street near Ontare Road and near Hope Avenue, and on Santa Barbara Street at Haley Street.

Tree-of-the-Month articles are sponsored by Santa Barbara Beautiful, whose many missions include the increase of public awareness and appreciation of Santa Barbara’s many outstanding trees and, in a long-time partnership with the City Parks & Recreation Department, the funding and planting of trees along the City’s streets – a project which has resulted in the planting, to date, of more than 12,000 street trees